JP3599288B2 - Image forming device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an image forming apparatus that forms an image using an inkjet recording method.
[0002]
[Prior art]
In an ink jet recording method in this type of image forming apparatus, several heaters are mounted in a nozzle filled with ink, and the heater is heated by applying a pulse signal to the heater to boil the ink. The ink is ejected by the bubble pressure generated by this. When used as an image forming apparatus, an image is formed by arranging several nozzles to form one head, and further forming several heads (for example, ink of cyan, magenta, yellow, black, etc.). ) To form a full-color image.
[0003]
In such an image forming apparatus, a control circuit for driving the head is configured as shown in FIG. FIG. 2 shows a case where one head is formed. In FIG. 2, reference numeral 201 denotes a shift register, 202 denotes a latch circuit, 203 to 206 denote AND circuits, 207 to 210 denote transistors, and 211 denotes a heater. Image data VDO is serial binary data from outside and is used as a transfer clock CLK. The data is transferred synchronously and serially / parallel converted by the shift register 201 sequentially. After 128 pieces of image data VDO (in this example, a head composed of 128 nozzles is used) are transferred, each of the nozzles is held by the LAT signal. In addition, one head composed of several nozzles is divided into n blocks (in this example, a head composed of 128 nozzles is divided into eight blocks and used), and one pulse of enable signal BENB0 is used for one block. To n and a pulse signal HENB for driving the heater, the transistor is turned ON only for the nozzles in which image data is enabled and held, and the heater is heated to discharge ink. With the above control, one line is printed as shown in FIG. 3, and several lines are printed in the main scanning direction to perform one band printing, and the paper is fed to perform the second band printing. An image composed of several bands is formed by repeating the process several times. In order to print at an accurate position with respect to the fluctuation of the carriage speed, a linear scale 401 having a slit for each dot is generally arranged as shown in FIG. Is read by a sensor 402 attached to the printer, and control for ejecting ink at an accurate position is performed by synchronizing ink ejection using the output signal. Further, as a configuration of the head, a type in which the head and the ink tank are integrated as shown in FIG. 5 (FIG. 5B) and a type in which the ink tank is arranged separately from the head (FIG. 5A) ), The head and ink tank are separately arranged, and only the ink tank can be replaced when the ink is consumed. However, the type with the head and ink tank integrated is treated as a consumable item. When the ink is consumed, it is arbitrarily replaced by the user's will.
[0004]
[Problems to be solved by the invention]
Conventionally, when an image is formed using an inkjet recording method, an image is formed using several heads as described above, and in the case of a configuration in which the head and the ink tank are integrated, When one or several heads have been replaced, a misalignment in the horizontal direction or a misalignment in the vertical direction between the heads occurs as shown in FIGS. Occasionally, streaks occur in the horizontal or vertical direction, resulting in image unevenness. In order to eject ink at an accurate position with respect to the main scanning position of the head, in a device that synchronizes ink ejection using a linear scale, when reciprocating printing is performed, as shown in FIG. However, there is a delay until the ink is ejected from the slit position, so that the ejection position is shifted and the image is sometimes uneven. This was particularly noticeable in the case of line art.
[0005]
The present invention has been made in view of the above, and an object of the present invention is to provide an image forming apparatus that accurately detects a head displacement when a head is replaced.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus that forms an image using a plurality of heads by an inkjet recording method, and a printing unit that prints a predetermined pattern by the plurality of heads. Reading means for reading a predetermined pattern printed by the printing means, and detecting means for detecting a shift amount of another of the plurality of heads with respect to a reference head from the pattern read by the reading means. It is the gist to have.
[0007]
An image forming apparatus according to the present invention is an image forming apparatus that forms an image using a plurality of heads by an inkjet recording method, and detects that at least one of the plurality of heads has been replaced. Exchange detecting means for performing, when the exchange detecting means detects that the head has been exchanged, printing means for printing two parallel patterns by the reference head and the other head of the plurality of heads; Reading means for reading the two parallel patterns printed by the printing means, position calculating means for calculating the position of the center dot of each pattern read by the reading means, and center of each pattern calculated by the position calculating means The width between the patterns of the reference head and the width between the patterns of the reference head and the other head are calculated from the positions of the dots, and based on the difference between the two widths. And summarized in that and a deviation calculating means for calculating a deviation amount of the head Te.
[0008]
Further, the image forming apparatus of the present invention is an image forming apparatus that forms an image using a plurality of heads by an inkjet recording method, and detects that at least one of the plurality of heads has been replaced. Exchange detecting means, and a printing means for printing a plurality of two parallel patterns by a reference head and other heads of the plurality of heads when the exchange detecting means detects that the head has been exchanged, Reading means for reading the plurality of parallel two patterns printed by the printing means; position calculating means for calculating the position of the center dot of each pattern read by the reading means; and each of the positions calculated by the position calculating means. Calculating the width between the patterns of the reference head and the average value of the width between the patterns of the reference head and the other head from the position of the center dot of the pattern , And summarized in that and a deviation calculating means for calculating a deviation amount of the head based on the difference between the width due to the average value.
[0009]
[Action]
In the image forming apparatus of the present invention, a predetermined pattern is printed by a plurality of heads, the printed predetermined pattern is read, and a deviation amount of another head from the read pattern with respect to a reference head among the plurality of heads is read. Is detected.
[0010]
Further, in the image forming apparatus of the present invention, when it is detected that the head has been replaced, two parallel patterns are printed by the reference head and the other heads of the plurality of heads, and the printed parallel pattern is printed. The two patterns are read, the position of the center dot of each read pattern is calculated, and the width between the reference head pattern and the width between the reference head and other head patterns is calculated from the calculated center dot position of each pattern. Is calculated, and the deviation amount of the head is calculated based on the difference between the two widths.
[0011]
Further, in the image forming apparatus of the present invention, when it is detected that the head has been replaced, two parallel patterns are printed by the reference head and the other heads of the plurality of heads, and the plurality of printed patterns are printed. Are read, the position of the center dot of each read pattern is calculated, and the width between the patterns of the reference head and the pattern of the reference head and other heads are calculated from the calculated position of the center dot of each pattern. An average value of the width between the heads is calculated, and the amount of head displacement is calculated based on the difference between the two widths based on the average value.
[0012]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus shown in FIG. 1 has an external device 101, a print control unit 102, and a head 103, and a linear scale 110, a sensor 111, and an upper cover open / close detection sensor 112 are connected to the print control unit 102. .
[0014]
In the embodiment shown in FIG. 1, control is performed to form an image on recording paper using the head 103 from image image data VDI transferred from an external device 101 such as an image scanner, a personal computer, and a CAD. In particular, the print control unit 102 generates a signal necessary for that. The print control unit 102 includes a CPU 109, a head control unit 105, a pattern detection unit 106, a pattern width detection unit 107, and a registration adjustment amount detection unit 108. Among them, the CPU 109 is an external device to which the serial image data VDI is transferred. An interface with the device 101 is performed, and the operation of the entire print control unit 102 such as each memory and I / O is controlled. When the serial image data VDI is transferred from the external device 101, the head control unit 105 temporarily stores the image data VDI for several bands in the image memory in accordance with a command from the CPU 109. The held image data VDI undergoes various image processing, and the image data VDO is output in accordance with the scanning of the head 103.
[0015]
In the present embodiment, a linear scale 110 is arranged as shown in the figure, and printing control such as output of image data VDO is performed by using a signal LINSCL output from the linear scale 110 in synchronization with scanning of the head 103. Is synchronized. In the head control unit 105, the enable signals BENB0 to BENB7 of each block of the head (in the present embodiment, since the head composed of 128 nozzles is divided into eight blocks, there are eight block enable signals. And a pulse signal HENB for driving the heater, which is necessary for ink ejection. The image data VDO, the block enable signals BENB0 to BENB7, the pulse signal HENB for driving the heater, and the like output from the head control unit 105 are transferred to the head 103. The control circuit in the head 103 controls each image data VDO and the enable signal (BENB). , HENB) are turned on, the heaters are turned on only for the nozzles that are enabled, ink is ejected and adheres to the recording paper to form an image for one line, and the above control is performed in the main scanning direction in the head 103. Are scanned to form an image image for one band.
[0016]
In the present embodiment, the head control unit 105 and the head are constituted by four circuits (pieces), and cyan, magenta, yellow, and black ink tanks are provided respectively (in the present embodiment, the head and the ink tank are It is full-color printing. In the following description, only one circuit (piece) will be omitted. The upper cover opening / closing detection sensor 112 is attached to the main body structure as shown in FIG. 7, and when the upper cover 91 is opened and the head 103 is replaced, the five patterns a are automatically set as shown in FIG. Is printed. In the present embodiment, the upper cover opening / closing detection sensor 112 constitutes a head replacement detecting unit, and it is assumed that the head is replaced when the upper cover 91 is opened. Further, a sensor 111 is attached near the head as shown in FIG. 7. After printing a pattern as shown in FIG. 8, each pattern is read by the sensor 111, and the registration adjustment amount is detected through the following process. Is
[0017]
First, the pattern a and b shown in FIG. 8 are scanned, the output of the sensor 111 is detected by the pattern detection unit 106 in the print control unit 102 where the pattern density changes, and the pattern width detection unit 107 Find the width of the pattern. Thereafter, the CPU reads the data of the width of each pattern and performs １ ／ calculation to calculate the center dot position of each pattern. Next, the same pattern is scanned again, and the width between the center dots is obtained using the data of the center dot of each pattern described above. With the above operation, the width between the center dots of each of the patterns a to c, a to d, and a to e is similarly obtained. After obtaining each of the above data, it is possible to calculate how much other heads are attached to the reference head by subtracting each data with reference to the data of the a and b patterns.
[0018]
Hereinafter, the operation of each unit will be described. First, the internal configuration and simple operation of the head 103 will be described with reference to FIG. As shown in FIG. 2, the head 103 includes a shift register circuit 201, a latch circuit 202, AND circuits 203 to 206, transistors 207 to 210, and a heater 211, and is synchronized with a transfer clock CLK from the head control unit 105. Then, the serially transferred image data VDO is converted into parallel data by the shift register 201, and when the 128 pieces of data are available, the latch 202 temporarily holds the data by the holding signal LAT. The held image data VDO is obtained by turning on the transistors only in the nozzles for which the block enable signals BENB0 to BENB7 generated by the head control unit 105 and the heater drive pulse signal HENB are enabled and the image data is enabled, the heater 211 is heated, and the ink 211 is heated. Is ejected, ink adheres to the recording paper, and an image is formed.
[0019]
Next, the internal configuration and simple operation of the head control unit 105 that generates a signal necessary for driving the head 103 will be described with reference to FIG. The head control unit 105 mainly includes an image memory 901, an image memory control unit 902, an image synchronization signal generation unit 903, and a heater drive signal generation unit 904. As described above, the image memory control unit 902 controls the memory for temporarily storing the serial image data VDI transferred from the external device 101 for several bands in the image memory 901 and scans the stored image data for the head 103. , Memory control for outputting the image data VDO to the head 103 is performed. When the image data VDI is input to the image memory 901, an address signal of the memory is generated in synchronization with the transfer timing of the data from the external device 101, the image data VD is sequentially stored, and the scanning of the head 103 from the memory is performed. , An address signal of the memory is generated in synchronization with the synchronization timing (HSYNCTRG) from the image synchronization signal generation unit 903, and the image data VD is output from the memory.
[0020]
As shown in FIG. 10, the image synchronization signal generation unit 903 includes an HSYNCTRG generation unit 1001, a counter 1002, comparators 1003 and 1004, AND circuits 1005 to 1008, and a CPU I / F unit 1009. Are generated, and a synchronizing signal HSYNCTRG for outputting the image data VD from the memory is generated using the signal LINSCL output from the linear scale 110. Further, the counter 1002 counts the synchronization signal HSYNCTRG, recognizes the scan position of the head, and compares it with the area data set by the CPU 109 to generate a print area signal WIND as shown in FIG.
[0021]
Further, when detecting the registration adjustment amount, the pattern printed on the printing paper when the pattern is scanned by the sensor 111 as shown in FIG. 12 and the mechanical member on the background of the paper cannot be recognized. It also generates a resist area signal REGIWIND. When the registration adjustment amount is detected, WIND is enabled, and when each of the ink discharge control signals (VDO, BENB, HENB, etc.) is output by the head control unit 105, the ink is discharged, so that the resist area signal REGIWIND Only the CPU is enabled and the CPU (REGIRD) is turned off.
[0022]
Further, the heater drive signal generator 904 generates a signal (block enable signals BENB0 to BENB7) for selecting which block of the head to drive and a heater drive pulse signal HENB in synchronization with the synchronization signal HSYNCTRG. I have. In the head 103, ink is discharged only from the nozzles for which the block enable signals BENB0 to BENB7, the pulse signal HENB for driving the heater, and the image data VDO are all enabled.
[0023]
Using the signals as described above, image data is printed, and as described above, when the head 103 is replaced, a pattern including five patterns a to e as shown in FIG. 8 is printed. Next, this pattern will be described with reference to FIG. In FIG. 8, patterns a / b are printed using a reference head, and c / d / e are printed using another head. In this embodiment, a / b is black, c is cyan, d is yellow, and a head provided with a black ink tank is used as a reference to match a head provided with another color ink tank with the head. e performs printing using a head provided with a magenta ink tank. Also, in FIG. 8, the pattern c / d / e is shifted from the pattern b, and the printing is to be performed on the same reference line. However, as shown in FIG. , The printing result shows a state in which the printing is performed with a shift. As described above, the pattern for detecting the displacement of the resist in the horizontal direction in FIG. 8 is printed as shown in FIG. 8A, and the pattern for detecting the displacement of the resist in the vertical direction is similarly shown in FIG. Print as in b). After printing the pattern as described above, each pattern is read using the sensor 111 attached near the head 103, and the registration adjustment amount is detected.
[0024]
Based on the output of the sensor 111, the pattern detecting section 106 in the print control section 102 detects a portion where the density of the pattern changes. FIG. 13 shows details of the pattern detection unit 106. In FIG. 13, reference numeral 1301 denotes an analog switch, 1302 denotes a differential amplifier, 1303 denotes a non-inverting amplifier, and 1304 denotes a comparator. The CPU turns on the analog switch 1301 when reading the background paper of the pattern. As shown in FIG. 14, a control is performed to reduce the output of the differential amplifier 1302 to GND with respect to the output of the sensor 111 that is input with a white level floating by about several mV. This is performed in order to accurately recognize the paper (white) and the pattern because the white level differs every time depending on the type of paper, floating paper, and the like.
[0025]
The output of the differential amplifier 1302 is amplified by the non-inverting amplifier 1303 to such an extent that the yellow pattern having the lowest input level can be distinguished from paper (white). The output of the comparator 1303 saturates), and is compared with a reference voltage which is a comparator 1304 and converted into binary digital data (REGIPT).
[0026]
The binary digital data (REGIPT) is then used to determine the width of each pattern by the pattern width detection unit 107, and the CPU halves the width data of each pattern to calculate the center dot position of each pattern. . FIG. 15 shows details of the pattern width detection unit 107. In FIG. 15, reference numerals 1501 to 1505 denote AND circuits, reference numerals 1506 to 1507 denote flip-flop circuits, reference numeral 1508 denotes an up / down counter, reference numerals 1509 to 1510 denote latch circuits, reference numerals 1511 to 1512 denote selectors, and reference numeral 1513 denotes a CPU I / F unit. As described above, since the pattern printed on the printing paper and the mechanical member on the background of the paper cannot be recognized, only the pattern signal is output by the AND circuit 1501 using the resist area signal REGIWIND output from the head control unit 105. It is controlled to be. After only the pattern is detected by REGIWIND, a load (LD) signal for operating the up / down counter 1508 is generated by the AND circuit 1503 and the flip-flop 1506. The input data of the counter 1508 is loaded at the beginning of each pattern, and control is performed so as to count up when the pattern is enabled. When the enable signal is terminated by the AND circuits 1502, 1504, and 1505 and the flip-flop 1507, two patterns are read from the output result of the counter 1508 every time the sensor 111 scans, so each pattern is latched by the latch circuits 1509 to 1510. To generate a sampling signal to be stored in the memory.
[0027]
After the pattern reading is completed, the CPU 109 reads the data of each of the latch circuits 1509 to 1510, and calculates the center dot position by halving each data. By doing so, even if the output level of the sensor slightly varies due to the type of paper, paper floating, sensor accuracy, etc., the center value is the same, so that a stable output result is always obtained. After calculating the center dot position, the data of each pattern is set in the selector 1511. After the setting is completed, the up / down counter 1508 and the selector 1512 are set to down count by the CPU (PW / PPWN is set to “L”), the same pattern is scanned again, and the up / down counter is set at the center dot position of each pattern. A borrow signal is output from the borrow signal (BO) output of 1508. This carry signal is the timing signal (CENTDT) at the center dot position of each pattern, and is output at the timing shown in FIG.
[0028]
Using the carry signal output from the pattern width detection unit 107, the registration adjustment amount detection unit 108 obtains the width between the center dots of each pattern. FIG. 16 shows details of the registration adjustment amount detection unit 108. In FIG. 16, reference numeral 1601 denotes a flip-flop, 1602 denotes a counter, and 1603 denotes a CPU I / F unit. The flip-flop 1601 is used based on a carry signal output from the pattern width detection unit 107 as shown in FIG. A width signal between the center dots of each pattern is generated, the width between the center dots is counted by the counter 1602, and after the reading is completed, the width data is read by the CPU. This data is the data (1) between the central dots of the patterns a and b in FIG. With the above operation, the width between the center dots of each of the patterns a to c, a to d, and a to e is similarly obtained. After obtaining each of the above data, calculating how much other heads are attached to the reference head by subtracting each data with reference to the data of the a and b patterns ((1)). Becomes possible. It is also possible to detect the direction of deviation by the sign (+/-) of the difference result.
[0029]
The above-described operation is performed on the pattern for detecting the lateral resist displacement shown in FIG. 8A and the pattern for detecting the vertical resist displacement shown in FIG. It is possible to detect a displacement due to the lateral mounting.
[0030]
In the above-described embodiment, the method of detecting the deviation of the vertical / horizontal registration by one detection operation has been described. However, in one detection operation, the fluctuation of the level of the sensor output signal due to the accuracy of the sensor 111 and the comparison in FIG. The detection result may fluctuate every time the detection is performed due to the fluctuation of the reference voltage of the detector 1304 and the temperature characteristics of each semiconductor used in the present embodiment. Therefore, to solve this problem, there is a method of increasing the number of detections and using the average value. In the case of using the circuit of the above embodiment, if the sensor 111 scans the same pattern many times, the number of detections is increased. Although it is possible to increase the number of detections, it is necessary to perform a considerable scan, so that the detection time is considerably long. Therefore, when the average value is used by increasing the number of times of detection, it is realized by changing the circuit 107 in FIG. 15 of the above embodiment to a circuit 107 ′ in FIG. 17 and increasing the print pattern as in FIG. Becomes possible.
[0031]
In FIG. 17, reference numerals 1701 and 1702 denote adders (in FIG. 17, the description of the same parts as in FIG. 15 is omitted), and a total of n times is calculated by repeatedly adding outputs of the latch circuits 1509 to 1510. Then, CPU divides by n and further halves to calculate the data of the central dot. Further, since the same pattern is read continuously as shown in FIG. 18, the total data for n times is also output to the output of the counter 1602 in FIG. 16, but the average value is calculated by dividing by n by the CPU. It is possible to do. By performing the above control, more accurate detection becomes possible.
[0032]
【The invention's effect】
As described above, according to the present invention, a predetermined pattern is printed by a plurality of heads, the printed predetermined pattern is read, and the read pattern is used as a reference for other reference heads among the plurality of heads. Since the amount of displacement of the head is detected, it is possible to accurately detect the displacement between the heads due to the mounting of the heads when the heads are replaced and the displacement occurring in reciprocating printing.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing details of an internal circuit of a head in the embodiment of FIG.
FIG. 3 is a diagram showing an example of a print result in the embodiment of FIG.
FIG. 4 is a diagram showing a configuration of a linear scale and slits in the embodiment of FIG. 1;
FIG. 5 is a diagram illustrating a configuration of a head and an ink tank.
FIG. 6 is a diagram illustrating a printing result when a head is shifted.
FIG. 7 is a view showing a main body configuration including an upper cover in the embodiment of FIG. 1;
FIG. 8 is a diagram showing a print pattern in the embodiment of FIG.
FIG. 9 is a block diagram illustrating a configuration of a head control unit in the embodiment of FIG.
FIG. 10 is a block diagram illustrating a configuration of an image synchronization signal generation unit used in the head control unit of FIG. 9;
FIG. 11 is an explanatory diagram showing definitions of a print area signal WIND and a synchronization timing HSYNCTRG.
FIG. 12 is an explanatory diagram showing the definition of a resist area signal REGIWIND.
FIG. 13 is a block diagram illustrating a configuration of a pattern detection unit in the embodiment of FIG.
FIG. 14 is an explanatory diagram showing a relationship between a print pattern and output signals of each circuit in the embodiment of FIG.
FIG. 15 is a block diagram showing a configuration of a pattern width detection unit in the embodiment of FIG.
16 is a block diagram illustrating a configuration of a registration adjustment amount detection unit in the embodiment of FIG.
FIG. 17 is a block diagram illustrating a configuration of a pattern width detection unit according to another embodiment of the present invention.
18 is a diagram showing a print pattern in the embodiment of FIG.
[Explanation of symbols]
101 External device
102 Print control unit
103 head
105 Head control unit
106 pattern detector
107 Pattern width detector
108 Registration adjustment amount detection unit
109 CPU
110 linear scale
111 sensor
112 Upper cover open / close detection sensor

Claims (5)

An image forming apparatus for forming an image by using a plurality of heads by the ink jet recording method,
And printing means for printing two parallel patterns by the plurality of heads,
A reading means for reading said two parallel pattern image printed by the printing means,
Position calculating means for calculating the center position of each pattern read by the reading means,
A shift calculating unit that calculates a shift amount of the head based on the center position of each pattern calculated by the position calculating unit ;
The printing means prints two parallel patterns at a predetermined interval by the reference head of the plurality of heads as the pattern, and prints two parallel patterns at the same interval by the reference head and another head. A pattern is printed, and the shift calculating unit calculates an interval between two patterns by the reference head and an interval between two patterns by the reference head and the other head based on a center position of each pattern obtained by the position calculating unit. And calculating the amount of deviation of the other head from the reference head based on the difference between the two intervals .   2. The image forming apparatus according to claim 1, wherein each of the two parallel patterns printed by the printing unit has the same width.   The printing means prints a plurality of the two parallel patterns by the reference head as a plurality of the two parallel patterns, and prints a plurality of the two parallel patterns by the reference head and another head. Calculates an average value of the interval between the two patterns by the reference head from the center position of each pattern calculated by the position calculation means, and an average value of the interval between the two patterns by the reference head and the other head; 2. The image forming apparatus according to claim 1, wherein a head shift amount is calculated based on a difference between both intervals based on the average value. Further comprising an exchange detecting means for detecting that at least one of the plurality of heads has been exchanged, and printing the two parallel patterns when the exchange detecting means detects that the head has been exchanged. and an image forming apparatus according to claim 1, 2 or 3 further characterized in that to calculate the shift amount of the read and the head. Said reading means performs the first and second scan with respect to the two parallel pattern, said position calculating means calculates the width and the center position of each pattern in the first scan, the deviation calculating means said first the image forming apparatus according to claim 1, 2, 3 or 4, wherein the calculating the distance of the center position as the interval of the pattern 2 of the scan.

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